U.S. patent number 4,956,036 [Application Number 07/244,364] was granted by the patent office on 1990-09-11 for method of making a power transmission belt including moisturizing and grinding.
This patent grant is currently assigned to The Gates Rubber Company. Invention is credited to Douglas R. Sedlacek.
United States Patent |
4,956,036 |
Sedlacek |
September 11, 1990 |
Method of making a power transmission belt including moisturizing
and grinding
Abstract
A method of making a power transmission belt with discontinuous
fibers by forming oppositely facing friction driving surfaces by
grinding such that fiber protrudes from the driving surfaces and is
bent exposing lateral side portions of fiber.
Inventors: |
Sedlacek; Douglas R.
(Englewood, CO) |
Assignee: |
The Gates Rubber Company
(Denver, CO)
|
Family
ID: |
26821089 |
Appl.
No.: |
07/244,364 |
Filed: |
September 15, 1988 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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122989 |
Nov 19, 1987 |
4798566 |
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Current U.S.
Class: |
156/137; 156/139;
156/154 |
Current CPC
Class: |
F16G
5/06 (20130101); F16G 5/20 (20130101) |
Current International
Class: |
F16G
5/06 (20060101); F16G 5/20 (20060101); F16G
5/00 (20060101); B29C 067/14 () |
Field of
Search: |
;156/137,138,139,140,142,154
;474/237,238,263,265,260,261,262,264,266,267,268 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0149443 |
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Nov 1980 |
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JP |
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0086648 |
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May 1982 |
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JP |
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Primary Examiner: Ball; Michael W.
Assistant Examiner: Maki; Steven D.
Attorney, Agent or Firm: Oberg, Jr.; H. W. Castleman, Jr.;
C. H.
Parent Case Text
This is a division of application Ser. No. 122,989, filed Nov. 19,
1987, and now U.S. Pat. No. 4,798,566.
Claims
What is claimed is:
1. In a method of making an elastomeric rubber-type power
transmission belt with an embedded load carrying section and an
elastomeric layer having dispersed discontinuous fiber oriented
transversely of the belt by grinding the elastomeric layer and
forming oppositely facing friction driving surfaces, the
improvement comprising the steps of:
dispersing discontinuous fiber in the elastomeric layer to a fiber
loading from about 1 to about 6 percent by volume, the fiber having
a greige tensile modulus sufficient to inhibit the fiber from being
severed during grinding;
forming oppositely facing friction driving surfaces while
moisturizing with a liquid and grinding elastomer away and leaving
portions of fiber protruding from the oppositely facing driving
surfaces;
said grinding bending a majority of protruding fiber portions and
exposing lateral side portions of fiber; and establishing part of
the friction driving surfaces with the lateral side portions of
fiber.
2. The method of claim 1 comprising dispersing discontinuous aramid
fiber in the elastomer layer.
3. The method of claim 1 comprising dispersing discontinous aramid
fiber in the elastomer, the fiber of the type as sold under the
trademarks KEVLAR, TECHNORA and TWARON.
4. The method of claim 1 comprising grinding oppositely facing
friction surfaces while forming a multi-ribbed belt.
5. The method of claim 1 comprising grinding oppositely facing
friction surfaces while forming a V-belt.
6. The method of claim 1 comprising grinding oppositely facing
friction surfaces while forming a joined V-belt.
Description
BACKGROUND OF THE INVENTION
The invention relates to endless power transmission belts, but more
particularly, the invention relates to what some in industry term
as "raw edge" belts where oppositely facing friction driving
surfaces are formed of an elastomeric body and in which are
dispersed transversely oriented fibrous members.
There are several belt configurations which have "raw edge"
friction driving surfaces defined as part of a layer where
discontinuous fiber is dispersed and transversely oriented in an
elastomeric matrix. An example of a joined belt utilizing fiber
dispersed in an elastomeric matrix is shown in U.S. Pat. No.
1,777,864.
An example of a "raw edge" V-Belt employing discontinuous fiber
dispersed in an elastomeric matrix is shown in U.S. Pat. No.
3,416,383. The fiber is transversely oriented at angles varying
from 90.degree..
Ribbed-belts also may have a "raw edge" construction and employ a
layered construction with discontinuous fiber transversely oriented
in an elastomeric matrix. U.S. Pat. No. 4,330,287 discloses such a
construction.
All of the foregoing patents disclose a construction where
generally the end portions of the dispersed fiber terminate or are
severed at their oppositely facing friction driving surfaces;
however, the '383 Patent further shows that portions of the "raw
edge" may wear at a faster rate than embedded fabric layers but not
faster than the surfaces where there is embedded fiber.
The friction characteristics of the driving surfaces for all of the
described belts may be modified by a construction where there are
discrete protrusions of fiber extending beyond an elastomeric
portion of the driving surfaces. The file history of the U.S. Pat.
No. 3,871,240 includes photomicrographs showing that end portions
of fiber are exposed at oppositely facing frictional driving
surfaces of the belt. As further explained in the '240 Patent, cord
or fabric at concentrations of 20 percent by volume are preferred
although concentration as low as 5 percent may be used. This Patent
also teaches, that fiber, when loaded in an elastomer at the
preferred concentrations, do not give the best results.
The preferred construction of U.S. Pat. No. 3,871,240 may not be a
suitable solution for all belt types because of the relative height
of the friction driving surfaces. For example, the use of cord or
fabric is not a desirable solution for a multi-ribbed belt because
of the relative small height of the ribs.
Another use of fiber at friction driving surfaces is shown in U.S.
Pat. No. 3,190,137. Flocked fiber is embedded and vulcanized into
peripheral sides of oppositely facing driving surfaces leaving very
little, if any protruding fiber.
SUMMARY OF THE INVENTION
A belt construction is provided which is suitable for various belt
forms with oppositely facing friction driving surfaces such as
V-belts, joined V-belts, and multi-ribbed belts. The power
transmission belt of the invention is of the "raw edge" type with
an elastomeric body in which is dispersed discontinuous fibers that
are transversely oriented in relation to a longitudinal axis of the
belt. Portions of fiber protrude from the body at the driving
surfaces and are bent so as to expose lateral side portions of
fiber which define part of the friction driving surfaces.
An advantage of the invention is that the lateral side portions of
fiber have a greater surface area than the generally end portions
of protruding fiber as disclosed and taught in the prior art.
Consequently lower loadings of fiber in percent by volume may be
used to alter the frictional characteristics of the oppositely
facing driving surfaces.
Another advantage is realized when in a multi-ribbed belt of the
invention is exposed to low angular frequencies of about 20 Hz and
high angular acceleration (e.g., angular accelerations up to 3,000
rad/sec.sup.2). The invention has the beneficial result of
substantially inhibiting pilling of the lateral surfaces at the low
frequencies. Consequently, belt life is improved in such
applications.
In accordance with the method of the invention, a high tenacity and
wear resistant fiber is dispersed in an elastomeric matrix of which
a body is formed. The matrix with dispersed fiber, is optionally
ground in the presence of a moisturing liquid and oppositely-facing
friction driving surfaces are formed. The fibers have sufficient
tensile modulus so as to inhibit them from being cut or ground off
at an elastomer interface during the grinding operation. The fibers
are bent along the driving surfaces and lateral side part
portions.
An object of the invention is to provide a belt construction where
discontinuous fiber may be effectively used to control the
frictional properties of a driving surface; a resulting advantage
of the invention is that discontinuous fibers may be used at a
volumetric loading of approximately half of that preferred as
taught in the prior art where end portions of fiber are
exposed.
Other advantages or objects of the invention will be apparent after
reviewing the drawings and description of preferred embodiments.
Although the invention is adaptable to power transmission belts in
general, a multi-ribbed belt is shown in detail for illustration
purposes wherein;
FIG. 1 is a schematic view showing a multi-ribbed belt of the
invention trained around grooved pulleys and tensioned with a
backside idler;
FIG. 2 is an enlarged fragmentary cross sectional view taken along
the line 2--2 of FIG. 1 showing the belt in free span;
FIG. 3 is an enlarged view taken generally along the line 3--3 of
FIG. 2 but showing a portion of the belt in partial isometric view
to further illustrate a friction driving surface;
FIG. 4 is an enlarged view taken along the line 4--4 of FIG. 3 and
showing protruding fibers bent to expose lateral side portions of
fiber at a frictional driving surface; cross hatching is not used
for clarity;
FIG. 5 is a view similar to FIG. 2 but showing a V-belt of the
invention; and
FIG. 6 is a view similar to FIG. 2 but showing a joined V-belt of
the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to the Figures, a power transmission belt 10 of the
invention with a multi-ribbed configuration is trained around
multi-grooved pulleys 12, 14 and tensioned by a backside idler 16.
The belt is fabricated using known techniques and has a tensile
member 18 or load carrying section that is sandwiched between a
first layer 20 forming the top portion 22 of the belt and a second
layer 24 in which is formed a plurality of circumferential ribs 26.
Any desired material may be used as the tensile member such as cord
of cotton, rayon, nylon, polyester, aramid, steel or even
discontinuous fibers oriented for load carrying capability. Any of
the suitable elastomeric materials may be used in constructing the
first and second layers. For example, elastomers such as synthetic
rubbers, natural rubbers, or blends thereof may be used. One or
more layers 28, 30, of a textile material may be embedded in the
top of the first layer to form a wear resistance surface such as to
accomodate backside idlers or pulleys in a drive system.
Discontinuous fiber 32 is dispersed in at least a major portion of
that part of the second layer which forms a body portion 34 having
oppositely facing friction driving surfaces 36, 38. The fiber
preferably has a length in a range from about 0.04 in. (1 mm) to
about 0.47 in. (12 mm); but more preferably, the fiber has a length
from about 0.16 in. (4 mm) to about 0.28 in. (7 mm); and most
preferably from about 0.16 in. (4 mm) to about 0.24 in. (6 mm).
It is important that the fiber have a greige tensile modulus
sufficient to inhibit the fiber from being severed at the
elastomer-fiber interface during a grinding operation when forming
the oppositely facing sides (which is hereinafter explained in
conjunction with the method of the invention). The fiber should
have good wear resistant qualities so that it is not substantially
worn away during belt use. Examples of fiber having suitable
tension modulus and wear resistant qualities are aramid fibers,
such as those sold under the trademark KEVLAR by du Pont de Nemours
& Company; the trademark TECHNORA as sold by Teijin of Japan;
and the trademark Twaron as sold by Enka of Holland [all having a
greige tensile modulus of at least about 9.times.10.sup.6 psi (6333
Kg/mm.sup.2)].
The elastomeric body portion is loaded with fiber preferably from
about 0.5 to about 20 percent by volume, and more preferably from
about 1 to about 6 percent by volume. Most preferably, the fiber
loading is about 3 percent by volume of the body portion (i.e.,
that portion of the body having the oppositely facing driving
surfaces).
The oppositely facing friction driving surfaces 36, 38 are formed
in such a manner as to leave portions of fiber protruding from the
elastomer at the oppositely facing driving surfaces. Most of the
fiber protrudes from about 0.004 in. (0.1 mm) to about 0.012 in.
(0.3 mm) from the elastomeric body. In contrast, new prior art
belts using cotton fiber have protruding portions from about 0.0026
in. (0.65 mm) to about 0.005 in. (0.13 mm). Thus, belts of the
invention have fiber protruding approximately twice as far as that
of known prior art belts.
The protruding fiber portions are bent 40 against the body in such
a manner as to expose lateral side portions 42 which define part of
the friction driving surface. As particularly shown in FIG. 4, most
of the fiber portions are bent substantially in the same general
direction leaving them oriented generally longitudinally 44 with
the belt driving surfaces. It is estimated that the lateral side
portions of fiber cover from about 15 percent to about 52 percent
of the driving surface area at fiber loadings from about 1.7
percent to about 6 percent by volume respectively.
Method
As previously mentioned, the elastomeric body with dispersed fiber
is ground to form oppositely facing friction driving surfaces. It
is already known to form oppositely facing driving surfaces by
grinding an elastomeric layer in which is dispersed discontinuous
fiber. An example of such a grinding process is disclosed in U.S.
Pat. No. 3,839,116. However, such known processes sever or
terminate the fiber at the elastomeric body so that substantially
only end portions of fiber are exposed.
As previously mentioned, it is important to have a fiber with a
sufficiently high greige tensile modulus to inhibit severing the
fiber at the elastomer-fiber interface during the grinding
operation. In accordance with the invention, discontinuous fiber,
such as aramid fiber, is dispersed in a elastomeric layer in known
fashion and oriented transversely of the belt. The body is ground
in the presence of a moisturizing liquid such as water soluable oil
or water. It is believed that the moisturizing liquid acts to
lubricate the fiber and. inhibit it from being severed at the
elastomer-fiber interface. The grinding operation also operates to
orient the fiber generally longitudinally along the driving surface
by bending the fiber and exposing lateral side portions.
The grinding operation may be used in defining opposite facing
frictional driving surfaces 44 of a V-belt 46 as illustrated in
FIG. 5 or the opposite facing frictional driving surfaces 48 of a
joined belt 50 such as illustrated in FIG. 6.
Use
In use, a multi-ribbed belt of the invention is used as in a
serpentine front end-drive of a firing diesel engine. During
operation of the engine, in such an application, low oscillatory
angular frequencies of about 25 Hz. are encountered along with
angular acceleration as high as about 3,000 rad/sec.sup.2. A belt
of the invention operated for 50 hours with no appreciable pilling
as measured by a weight loss of only about 1 percent, and the
protruding fiber remained substantially intact. Comparatively, a
prior art belt with discontinuous cotton fiber (flock) was operated
on the same engine for 50 hours where there was significant pilling
as measured by a belt weight loss of about 9.7 percent; the
portions of protruding cotton fiber was worn away to the
elastomeric body.
A peculiar problem associated with multi-ribbed belts is that of
"pilling buildup" between adjacent ribs where pills accumulate and
are retained. Because of this, "weight loss" is not always a
totally accurate measurement. Nevertheless, belts of the invention
exhibited substantially no "pilling buildup" whereas the prior art
belt exhibited "pilling buildup" accompanied with substantial
weight loss.
The improved performance of the belt of the invention is attributed
to the exposed lateral side portions of fiber which define part of
the friction driving surface. As a fiber loading of about 5.2
percent by volume, the lateral side portion of fiber covers about
45 percent of the friction driving surfaces which is about 3 times
greater than a prior art belt having substantially the same loading
of cotton fiber.
The foregoing detailed description is made for purpose of
illustration only and is not intended to limit the scope of the
invention which is to be determined from the appended claims.
* * * * *